我有我在Excel 2013通过与VC2013内置一个DLL使用C ++函数：
double my_function(double input) {
//do something
return input*input;
}
在Excel VBA我有这样的这样的功能：
Declare Function my_function Lib "DLL_with_my_function.dll" (ByVal input As Double) As Double
这种运作良好，到目前为止，但是，现在，我希望能够返回第二个资料片，说的错误代码，通过第二个参数。 理想的情况是该错误代码将必须是输出至细胞在Excel，或至少通过debug.print控制台的能力。 我停留在使整个事情的工作和有Excel中崩溃了好几次。 这是我徒劳的尝试：
double my_function(double input, long *error_code) {
*error_code = 5;
return input*input;
}
#in Excel:
Declare Function my_function Lib "DLL_with_my_function.dll" (ByVal input As Double, ByRef error_code as long) As Double
当我打电话从工作表中的功能和指示细胞作为第二个参数的Excel崩溃我。 什么是正确的，优雅的方式来做到这一点？
你只是不能给EXEL细胞只要数到C \ C ++，因为它不会自动转换
你可以这样做：
double my_function(double input, long *error_code) {
*error_code = 5;
return input*input;
}
//unless you don't want to build the long from bytes, you can use function to do so.
long get_error_code(long* error_code ){
return *error_code;
}
在Excel中宣布新的功能太：
Declare Function my_function Lib "DLL_with_my_function.dll" (ByVal input As Double, ByVal error_code as long) As Double
Declare Function get_error_code Lib "DLL_with_my_function.dll" (ByVal error_code as long) As Long
#now in the function you should allocate memory to the error code:
Dim hMem As Long, pMem As Long
#hMem is handle to memory not a pointer
hMem = GlobalAlloc(GMEM_MOVEABLE Or GMEM_ZEROINIT, 10)
#pMem is your pointer
pMem = GlobalLock(hMem)
#now you can call to my_function with the pointer:
retval = my_function(input, pMem)
#in VB there is auto cast so this will work:
YourCell = get_error_code(pMem)
# Unlock memory make the pointer useless
x = GlobalUnlock(hMem)
# Free the memory
x = GlobalFree(hMem)
